Aerofoil



AEROFOIL Oct. 4, 1932. F. R. MAXWELL, JR

Filed Oct. 16. 1928 Patented Oct. 4, 1932 UNITED STATES PATENT; OFFICIEy AEROFOIL application mea october' 1s, 192s. smal 1ra. 312,862.

It is well known that aerofoils must beshaped differently for speed on the one hand and for lifting-power and ability to take-off at low speed on the other hand, aerofoils dcl. signed for speed having relatively low lifting-power and requiring relatively high takeolf speed. Various attempts have been made to provide aerofoil constructions which afford high velocity in flight and at the same time m are adjustable to permit low speed take-off and to afford a high degree of lifting-power, a typical example being disclosed in Patent No. 1,353,666. However, these constructions have not been satisfactory chiefly for the rea- 154 son that the do not increase the lifting-power suiicient j and the mechanical complications offset the relatively small aerodynamic advantage. l

Objects of the present invention are to provide aerofoils which afford high velocities and which at the same time may be readily adjusted to afford greatly increased liftingpower and to take-off at greatly reduced ,speed, which are substantially as strong and rigid as an ordinary wing built solely for one of the aforesaid types of service, which may afford substantially as high velocities as wings built solely for speed, which permit .the use of the best known conto-urs of both 4the upper and lower-surfaces of aerofoils, which may be adjusted for either type` of service either automatically or manually, or partly automatically and partly manually, and which are generally superior to aerofoils heretofore proposed for the'aforesaid uses.

For the purpose of illustration a concrete embodiment of the invention is shown in the accompanying drawing in which Fig. 1 is a fore-and-aft vertical section and Fig. 2 is a plan view.

The particular embodiment of the invention chosen for the purpose of illustration comprises an aerofoil having a forward part 45 l'bounded by surfaces 2 and 3, a rearward part 4 bounded by surfaces 5, 6 and 7, the two parts defining therebetween a slot 8 which extends obliquely through the wing, an ordinary flap 9, and upper and 'lower covers 10 and 11 for the slot 8. The forward part is small compared with the rearward part and, while it may be hollow, as shown in Fig. 1, comprises the forward spar. The other spars in the rearward part 12 and 13 may be rigidly connected toether and to the for-. ward and drag-bracing wires26 which extend across said slot. While the rear face 5 of slot 8 vmay also comprise the face of a spar, the second spar 12 is preferably located in the rear of the slot, in which case the wall 5 may be 00 formed of duraluminum or other suitable maf terial rigidly connected with spar 12. If the upper and lower coverings 6 and 7 are also formed of duraluminum or other rigid material, the wall 5 may comprise an integral 05 bridge or junction between these coverings. The upper cover 10 is hinged to the forward part 1 preferably in the region of the tip of the nose, and in the illustrated embodiment the hinge 14 is located under the nose. Thus, 7 while the cover 10 preferably conforms to the shape of the aerofoil, it determines the contour of the nose and, when raised, varies the fore-and-aft shape of the forward portion of the wing. The cover 10 may extend rearwardly beyond the slot 8 to any desired degree but in any case should overlap the rearward part of the wing to some extent. The lower cover 11 may be hinged on the same pintle at 14 to swing from the closed position shown in broken lines to the open position against the front wall 3 of the slot. Both covers may be formed of sheet duraluminum of the requisite thickness or of other lsuitable material and construction. A fairing piece 15 may be hinged at 16 to form a continuation of wall 8 when cover10 is raised, thereby preventing eddies under the cover.

While one or both of the covers may be closed automatically by springs after climb- 9 ing to the desired elevation, manual controls are preferably provided. Thus, in the illustrative embodiment, arm 17 pivoted to spar 12 at 18 is adjustably connected to cover 10 through links 19 and to cover 11 through 95 links 20 and 21, the pin connections between I arms 17 and links 19 and 2() permitting ad justment of the movement of each'cover in response to predetermined movement of the arm. Thel Opening effect of link 19 may be 10 spar in any suitaile manner as by ribs 65 supplemented by additional means such as link 22 and cam 23 pivoted in a recess 24' in the forward part of the wing. The Cam 23 may be shaped to increase the flexure of the cover as the cover is raised, thereby increasing the camber of the aerofoil, or merely to supplement the link 19 without varying the camber. The aforesaid actuating arms, links, etc., may be duplicated at suitable intervals throughout the length of the wing and may be interconnected to move in unison Vby rigidly mounting all the arms 17 on a common shaft at 18. One or both of the slot covers may be' interconnected with the fia-p 9 so as to operate in unison therewith 1n response to a single control, a suitable interconnection being shown in Fig. 1 in the form of ayconnecting rod 25. The usual control cable or wire 4(not shown) may be connected to the shaft 18, rod 24, or directly to the flap in the usual manner.

From the foregoing it will be understood that the covers 10A and 11 are opened when increased .lifting-power is desired, as when rising, and then closed when the desired altitude-is attained. Tests of afvwing shaped as illustrated, which corresponds to a well. known standard, show a lifting-power far in excess of any previous wing .of this type. The phenomenal performance of this wing is believed to ybe due chiefly to the superior shape and increased length of the slot made possible by this unique construction. It will be noted that this result is obtained without altering the elevation of the forward part of the wing relatively to the rearward part and without altering the under side of the wing, except of course to the extent of opening the slot. It will also/,be observed that the slot gradually decreasesin width from the bottorn upwardly along smoothly curving lines, the curvature of the rear wall 5 being greater than that of the front wall 3. By raising the cover 1U at the same time the flap 9 is lowered, the camber and angle of incidence of the aerofoil is increased simultaneously with the uncovering of the slot as claimed in my prior Patent No. 1,456,643.

1. An'aerofoil comprising a'forward spar forming a leading edge and a rearward part rigidly interconnected as a unitary wing, the two parts being spaced in approximate parallelism to provide therebetween a slot eX- tending `obliquely-through the aerofoil, and a cover for the slot hinged at one edge i thereof on said forward spar beneath the leading edge of said spar and curving forwardly, upwardly and thence rearwardly 4over said spar and the slot.

2.- An aerofoil comprising forward and rearward parts rigidly interconnected by rib-like members as to form a unitary wing, the two parts being spaced to provide there:- betweenfa slot extending obliquely through the aerofoil, and a cover for the slot hinged onl said forward part forwardly of the trailing edge of the forward part, said cover when closed tting the contour of the -ae1'o' foil and when open inclining upwardly from a line in advance of said edge, and a fairing piece hinged on said forward part toubridge the space between said edge and cover when opened.

An aerofoil comprising forward and rearward parts rigidly interconnected by spacing members to form a unitary wing, the two parts being spaced to provide therebetween a slot extending obliquely through the aerofoil, a cover for theslot hinged 'on said forward part in the region of the leading edge of the forward part, 'said cover when closed covering` the forward part and the slot and when open inclining upwardly, along a continuous stream-line contour, from said region to the rear of said slot, and a fair- Oing piece hinged to the trailing edge of said forward part to swing upwardl and bridge the space between said trailinge ge and cover when open, along a contour forming a 'smooth continuation of the forward side of said slot.

c 4. An aerofoil comprising forward and rearward parts rigidly interconnected kas a unitary wing, the two parts being spaced to provide therebetween a slot extending obliquely through the aerofoil, a cover for the slot hinged on said forward part to inoline upwardly and rearwardly when opened, said cover when closed conforming to the stream-line contour of the aerofoil and when o en extending rearwardly and upwardly a ove the normal outline of the aerofoil, a cover hinged4 to said forward part at the lower end of the slot, the latter cover being shaped to conform to the contour of the. underside of the aerofoil when closed and swinging against the forward side of said slot when opened, the two covers being pivotally interconnected to open and close in unison, and a iap co-operable with the first mentioned cover to effect a stream-lining of the under side thereof when in open position.

5. In combination with an aerofoil, a cover member hingedly supported in advance of the leading edge of said aerofoil and movable to one position to effect a streamlined forward extension of the upper surface of said aerofoil and to another position in which its rear edge isspaced vertically relative to said leading edge, a second cover member hingedly supported in advance of said leading edge and movable to one position to effect a streamlined forward extension of the lower therefrom by an upwardly and rearwardlg extending slot, and a flap co-operable wit v the first mentioned cover to e'ect a streamlining of said slot.

6. An aerofoil comprising a forward spar forming a leading edge, a main spar, a rear spar, a plurality of ribs connecting said spars in spaced substantially parallel relation, a skin coverin for said aerofoil terminating in spaced re ation to said forward spar so as to provide a slot therebetween, upper and lower flaps pivoted to said forward spar on a common axis, and means for moving said flaps to close said slot.

,5 Signed by me at Boston, Massachusetts,

this 11th da of October, 1928.

F ANK R. MAXWELL, Jn. 

